Hadlyme Formation of Waterford Complex here defined in the Avalon terrane of eastern CT to include three extrusive volcanic facies: North Plain, Jennings Pond, and Mansfield Hollow lithofacies. Term lithofacies, rather than member, used to convey vertical or chemical continuity, not lateral continuity. Jennings Pond lithofacies is a bimodal unit containing a medium-gray-weathering plagioclase-quartz-biotite gneiss and a dark gray to black amphibolite. Easily recognized in the field by its high amphibolite content. Lower contact defined as the base of the lowest thick amphibolite. Thickness 14.9 m in drill core at Gillette Castle State Park. Lies between Tatnic Hill and Hebron Formations. Rocks previously mapped as part of Putnam Gneiss or Tatnic Hill Formation (Lundgren, 1963, 1964).

Source: GNU records (USGS DDS-6; Reston GNULEX).